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%I #9 May 17 2018 08:11:36
%S 6,12,24,42,60,84,114,144,180,222,264,312,366,420,480,546,612,684,762,
%T 840,924,1014,1104,1200,1302,1404,1512,1626,1740,1860,1986,2112,2244,
%U 2382,2520,2664,2814,2964,3120,3282,3444,3612,3786,3960,4140,4326,4512
%N Number of -n..n arrays x(0..2) of 3 elements with zero sum, and adjacent elements not equal modulo three (with -1 modulo 3 = 2).
%C Row 3 of A199909.
%H R. H. Hardin, <a href="/A199910/b199910.txt">Table of n, a(n) for n = 1..200</a>
%F Empirical: a(n) = 2*a(n-1) -a(n-2) +a(n-3) -2*a(n-4) +a(n-5).
%F Empirical g.f.: 6*x*(1 + x^2) / ((1 - x)^3*(1 + x + x^2)). - _Colin Barker_, May 17 2018
%e Some solutions for n=6:
%e ..0...-1....4....6...-1....4...-3...-6....6...-2....2....3...-5....6....2...-2
%e .-5....1...-6...-2....0...-1....1....1...-4....5...-2...-2....3...-5...-5....2
%e ..5....0....2...-4....1...-3....2....5...-2...-3....0...-1....2...-1....3....0
%Y Cf. A199909.
%K nonn
%O 1,1
%A _R. H. Hardin_, Nov 11 2011
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